> suppose that I make the FS twice as slow as before by meddling with> it to make it sharable>> then I simply share it among 4 nodes to get a two times _speed up_> overall.>> That's the basic idea. Details left to reader.

The "detail" is lock contention. If you lock the filesystemand invalidate the caches you'll be able to do one operationevery disk seek, across all nodes.

Chances are your 4-node system would have lower aggregatethroughput than a single node system.